714. Analysis of the Effect of Urine on the In Vitro Activity of Gepotidacin and Levofloxacin Against Escherichia coli, Staphylococcus epidermidis, and Staphylococcus saprophyticus

BACKGROUND: Gepotidacin (GSK2140944) is a first in class novel triazaacenaphthylene bacterial type II topoisomerase inhibitor in clinical development for the treatment of gonorrhea and uncomplicated UTI (acute cystitis). Gepotidacin selectively inhibits bacterial DNA gyrase and topoisomerase IV by a unique mechanism not utilized by any currently approved therapeutic agent and demonstrates in vitro activity against most target pathogens resistant to established antibacterials, including fluoroquinolones. This study was undertaken to determine the effect of various urine parameters on the in vitro activity of gepotidacin and a comparative agent, levofloxacin, against a variety of bacteria. METHODS: Study strains were tested according to the reference CLSI broth microdilution method using cation-adjusted Mueller–Hinton broth (CAMHB) and the following method variations: CAMHB with 25%, 50%, and 100% urine (not pH adjusted) and 100% urine (pH adjusted to 7.2–7.4, and 8). Quality control strains were concurrently tested each day. RESULTS: MIC endpoints in the reference method and in 100% urine were easily determined (i.e., clear buttons of growth up to the first well of no growth). Gepotidacin MIC results are summarized in the table. For E. coli and S. saprophyticus, there was a trend for higher gepotidacin MIC results with the addition of increasing amounts of urine. However, the increase was minimal such that mean dilution differences were ≤ 1.54. Against S. epidermidis, gepotidacin MICs were not significantly impacted by the addition of urine as 100% of urine condition MICs were within ±1 doubling dilution of the reference method MIC. The gepotidacin results for E. coli indicate that the average 1–2 dilution MIC increase observed in the unadjusted 100% pooled urine MIC may be associated with lower pH. A similar increase in levofloxacin MIC results for E. coli were also associated with pH, but at the higher pH of 8.0. In contrast, the increase in MIC observed in both the gepotidacin and levofloxacin S. saprophyticus results in 100% pooled urine do not appear to be a function of pH. CONCLUSION: Overall, the effect of urine on the gepotidacin and levofloxacin MICs was minimal and not inclusive of all strains tested. [Image: see text] DISCLOSURES: All authors: No reported disclosures.